1. Field of the Invention
The present invention relates to the use of adjuvants in topical ophthalmic compositions. In particular, this invention relates to the use of a combination of gelling polysaccharides and finely-divided drug carrier substrates in the compositions and a method for the controlled administration of a drug to patients wherein the compositions are administered as liquids which thicken to form gels upon instillation into the eye.
2. Description of the Related Art
There have been a multiplicity of liquids, ointments, gels and inserts used as vehicles in topical ophthalmic formulations. Liquid compositions for drop-wise instillation to the eye provide for easy formulation, but do not provide an accurate dosage amount, as portions of the liquid are often blinked away during their administration. Ointments and gels, while providing more accurate administration, often interfere with a patient's vision. Ocular inserts, both bioerodible and non-bioerodible, are also available and allow for less frequent administration of drug; however, these inserts require complex and detailed preparation. An additional problem with the non-bioerodible inserts is that they must be removed after use.
U.S. Pat. Nos. 4,136,173 (Pramoda, et al.), 4,136,177 (Lin, et al.) and 4,136,178 (Lin, et al.) disclose the use of therapeutic compositions containing xanthan gum and locust bean gum which are delivered in liquid form and which gel upon instillation. In these three patents, the mechanism for transition from liquid to gel is due to a change in pH.
U.S. Pat. No. 4,861,760 (Mazuel, et al.) discloses ophthalmological compositions containing gellan gum which are administered as non-gelled liquids and which gel upon instillation due to the change in ionic strength.
Commonly assigned U.S. patent application Ser. No. 07/641,214, filed on Jan. 15, 1991, discloses ophthalmic formulations containing carrageenans and furcellarans (hereinafter collectively referred to as "carrageenans") which are administered as partially gelled liquids which gel upon instillation into the eye.